Typically, chassis and heat sinks of electronic devices have heat generating parts that are produced from metals. Metals are used for such parts because of their thermally conductive nature. Metals dissipate received heat to the surrounding area very rapidly as compared to other materials. Therefore, metals can maintain the electronic parts, which are sensitive to heat, under high temperature conditions. In addition, metals have high mechanical strength and can be readily processed using sheet metal, die and cutting processes. Thus, metals are suitable materials for use as heat sinks, the shape of which can be complex.
However, it can be difficult to make heat sinks made of metal light weight because of the high density of metal. Moreover, processing costs can be high with metals.
Therefore, thermally conductive materials using synthetic resins have been developed to replace metals. For example, a thermally conductive resin could be used to make heat dissipation sheets or heat dissipation grease on printers, copiers, notebook computers, and the like.
Recently, it has been found that increased heat is generated by electronic devices because of their highly integrated nature and high performance. Moreover, as devices become thinner or lighter weight, the problem of dissipating generated heat is pronounced. At times, serious problems can arise in electronic devices due to locally generated heat, which can ultimately cause malfunction or burning of the devices. However, thermally conductive resins developed so far have low thermal conductivity, and accordingly there remains a need to solve the afore-mentioned problems using resins.
When thermally conductive insulating fillers are used in a large quantity in order to increase the thermal conductivity of the resin composition, the viscosity increases which in turn impairs the fluidity. As a result, articles cannot be produced by the injection molding process. In addition, the strength of the final product is not satisfactory. Therefore, it is important to form an efficient network of fillers inside the resin to maximize the thermal conductivity, while minimizing the amount of fillers. Sometimes a resin with a far lower viscosity is used in order to avoid impairing the fluidity during an injection molding process, even if the filler is added in a large quantity. However, resins with lower viscosity have low molecular weight which increases the reactivity between the molecular chains. This in turn can lead to hardening during the extrusion or injection molding process.
As a result, it is important to ensure the fluidity to form an efficient network of fillers so as to produce a resin composition having a high thermal conductivity and which makes injection molding possible. Further, the viscosity of the resin should be reduced and the stability during the process should be maintained.
In order to improve the thermal conductivity, carbon or graphite fillers have been used. However, although these fillers have a high thermal conductivity by themselves, they cannot be used in technological fields such as luminaries or electronic devices where electrical insulation property is required, because these fillers also have electrical conductivity.